The goal of the proposed research is the delineation of the scope, mechanism, and synthetic utility of the (3,3)sigmatropic rearrangement of N-vinyl (and aryl)-O-vinyl-hydroxylamines and related compounds. The proposal is advanced that this highly exothermic transformation (simply referred to as the 6-aza-Claisen rearrangement) may be a key reaction in chemical carcinogenesis initiated by certain aromatic hydroxylamines and hydroxamic acids. The feasibility of this proposal is to be evaluated by study of the reaction between 2-amino-6-chloropurine and appropriate N-aryl hydroxamic acids. The 6-aza-Claisen rearrangement is expected to afford a valuable synthetic method for intramolecular C-C bond formation under mild conditions. The resulting 1,4-imino ketones may be cyclized directly to heteroaromatic products or hydrolyzed to 1,4-diacarbonyl compounds. Synthetic routes to N-vinylhydroxylamines and N-vinyl hydroxamic acids are suggested since compounds of these types are virtually unknown. Several methods for the generation of the labile O-vinyl derivatives of N-vinyl (and aryl) hydroxylamines and hydroxamic acids are presented. The mechanism of the 6-aza-Claisen rearrangement is to be investigated by means of labelled substrates, substituent effects, and the effects of possible catalysts.